It is known in the art to measure force applied to a beam by means of strain gauges, especially in weighing scales. In some cases the load is applied to the beam by knife edges on the beam cooperating with V-bearings as shown, for example, in U.S. Pat. No. 2,598,812. In other cases with which the present invention is specifically concerned, the load is applied to the beam by forming a frusto-conical hole in the beam and exerting a pulling force against the sides of said hole by a member connected indirectly to the load as illustrated, for example, by the platform-type weighing scale in U.S. patent application Ser. No. 794,058 filed May 5, 1977 now matured into U.S. Pat. No. 4,153,125.
One difficulty with an apparatus of the latter type or any apparatus such as a torque measuring apparatus wherein the load is applied indirectly through the sides of a hole in the cantilever beam resides in the fact that the method used in applying the load in this manner can result in inaccuracy because the strain is directly proportional to the effective length of the beam and any change in length directly affects the strain or elongation. If the method of applying the load, therefore, changes the effective length of the beam, the resultant measurement as, for example, in a weighing scale or torque measuring device, will be inaccurate.